A rotary valve is a valve that rotates intermittently to control fluid flow. A rotary valve typically includes a track plate, a rotor plate, and an upper pressure-tight shell or casing. The casing and the trackplate form a fluid-tight housing totally enclosing the rotor plate. The rotor plate is maintained in fluid-tight contact with the track plate, and rotates in a horizontal plane. It has a slick, smooth surface, referred to as a “seal surface”, and a number of channels and holes and/or ports that communicate with corresponding channels, holes and/or ports in the trackplate, in order to direct the flow of fluid within the valve.
Wear and tear to the surface of the trackplate during use can cause it to be damaged to such an extent that the necessary sealing required for proper fluid control is impaired. Such damage can be caused by corrosion, erosion, friction, or distortion, or by the presence of foreign objects. Once the surface is damaged, either repair or replacement is necessary to reestablish an acceptable seal, so that the function of the rotary valve for the particular fluid control application is not affected. To avoid the significant cost of replacing a worn workpiece, the surface of the workpiece is refinished, by a process commonly referred to as ‘resurfacing.’
Although portable-lapping machines can be used to repair and refinish a workpiece surface in the field, they are suitable only for minor repairs. When the workpiece has been heavily damaged, or when precision resurfacing is necessary, lapping is impractical due to its limited capabilities for precision refinishing, excessive time, and wear to the parts. This is because the lapping machine's grinding and resurfacing apparatus produces an irregular surface finish, causing an ineffective seal within the rotary valve.
When use of a lapping machine is unsuitable, the trackplate must be removed and outsourced for resurfacing. This involves removing the trackplate, and shipping it to the site of a specially designed resurfacing machine. Trackplates used in large rotary valves are difficult to remove due to the size of the valve itself, and shipment is expensive and slow. Thus, in the case of rotary valves that are very large, such as those used in petrochemical refineries, this process is extremely costly and time consuming, thereby causing the refinery lost production time. It is therefore desirable to develop a resurfacing apparatus that can be used for precision resurfacing of heavily damaged workpieces “in situ,” that is, while remaining on-site at the location where the rotary valve is installed, and preferably, to further develop a process for resurfacing the surface of the trackplate without removing it from the rotary valve.